PROJECT SUMMARY The Planar Cell Polarity (PCP) component Vangl is overexpressed in a variety of carcinomas, and evidence is accumulating that Vangl-dependent PCP signaling may mediate cell migration and invasion resulting from induction of the epithelial-mesenchymal transition (EMT) program in breast cancer. For example, it has been reported that Vangl1 is up-regulated in 5% of invasive breast carcinomas and knockdown of Vangl1 in vitro impairs the migration of invasive MDA-B-231 breast cancer cells. Coupled with independent observations that EMT induction results in transcriptional expression of the PCP signaling ligand Wnt5a, these observations raise the possibility that Vangl-dependent PCP signaling contributes to cell migration and invasion resulting from activation of the EMT program. The studies outlined here seek to rigorously assess the role of Vangl proteins in breast cancer cell migration and invasiveness, and the contribution of Vangl-dependent PCP signaling to EMT driven cell migration and invasion. Specific Aim 1 will characterize the involvement of Vangl- dependent PCP signaling in breast epithelial and carcinoma cell migration and invasion in vitro. In these experiments breast epithelial and both non-invasive and aggressive carcinoma cells lines will be used to assess migration, invasion, and proliferation in response to stable Vangl overexpression or knockdown in vitro. Specific Aim 2 will characterize the contribution of Vangl-dependent PCP signaling to EMT-driven cell migration an invasion. Here, cell lines will be stably transduced with EMT-inducing transcription factors to assess the contribution of Vangl-dependent PCP signaling to EMT-driven cell migration and invasion in vitro. Specific Aim 3 will determine whether Vangl-dependent PCP signaling contributes to breast cancer cell migration and invasion in vivo. Conditional knockout Vangl mice crossed with a mouse mammary tumor model will be used to assess the effect of Vangls on tumor latency, size, and rate of metastasis will be measured. The successful completion of the proposed studies could implicate Vangl proteins and the Vangl-dependent PCP signaling pathway as a novel target for future therapeutic intervention in aggressive and metastatic breast cancer. Training opportunities for the PI include classes in mouse biology, cancer biology, pathology and surgery, weekly meetings with the UCD mammary gland biology and pathology group, an extensive series of seminars, tumor boards and symposia in cancer biology and therapeutics, and close collaborations with statisticians. Results emerging from the study will be presented at a national conference in cancer biology in Year 3.